Preparation of alkyl aluminum halides



Patented Feb. 3, 1942 Robert Buthrumflhicago, Ill.

No Drawing.

16 Claims. This invention relates to the preparation of alkyl aluminum halides higher than the methyl derivatives. y

One object .of this invention is to provide simple and convenient methods for the prepara- -tion of alkyl aluminum halides higher than the methyl derivatives. A further object of this in-- vention is to provide a continuous process for the preparation of alkyl aluminum halides higher than the methyl derivatives. Another object of this invention is to provide methods for the economical production of alkyl aluminum halides higher than the methyl derivatives. Other ob- -jects of this invention will become evident from the following description.

A large number'of alkyl aluminum-halides are theoretical: capable of existence and many have been synthetically prepared and characterized. All these compoimds may be represented by the general formulae: RAlXz and RzAlX, and,

where R represents alkyl groups such as methyl,

ethyl, prqpyl,.isopropyl, normal butyl, secondary butyl, tertiary butyl and the like and X represents halides such as chloride, bromide, iodide, fluoride. In alkyl aluminum halides containing two alkyl groups, said groups may be identical or difierent; likewise in alkyl aluminum halides containing two halide atoms, said atoms maybe identical or difierent. Accordingly, such compounds as methyl ethyl aluminum chloride, ethyl aluminum chloro-bromide, ethyl isopropyl alumi- 1 num bromide. and the like are theoretically possible or actually known.

A few methodsliterature but up to the present time the preparation involving the interaction of alkyl halides with metallic aluminum has probably been the most widely used.v For example, Hnizda and Kraus have recently-described such a method in the Journal of'the American Chemical Society,- volume 60, page 2276, 1938. According to these investigators, the desired compounds are produced by contacting an alkyl halide with metallic aluminum promotedwith a trace of an aluminum halide or an alkyl aluminum halide from a previ-' ous preparation. The reaction, after once being started, is autocatalytic and highly exothermic so that cooling must be applied. According to these investigators, the reaction should be conducted at a temperature of 75 C. or below.

While the above method of preparation is very convenient and hence excellently suited for use on the laboratory scale, it is evident that it requires the use of relatively expensive alkyl for the preparation of alkyl aluminum halides have been described in the Application September 27', 1939. Serial No. 296,807

and metallic aluminum in the Journal of the Technologists, volume described an imhalides. Hall and Nash, Institution of Petroleum 23, pages679 to 687, 1937, have proved method for the preparation of ethyl aluminum dichloride and diethyl aluminum chloride by a reaction involving the contacting of ethylene with a mixture of aluminum chloride at high pressures and moderate temperatures. While by this procedure, the use of the relatively expensive alkyl halides is eliminated, the yields of the desired compounds are rather low, the ethyl aluminum dichloride and diethyl aluminum chloride being contaminated with 50% by volume, or more, of heavy hydrocarbons.

I have found that on contacting a mixture of hydrogen and an olefine or cleflnes with a mixture of an aluminum halide andvmetallic aluminum, especially metallic aluminum in the activated state, greatly improved yields of alkyl aluminum halides higher than the methyl derivatives over those hitherto known are obtained. The reaction proceeds approximately in accord with the equation:

CaHEn-H where X represents a halide and n is a positive whole number greater than unity, The necessity for an outside supply .of hydrogen for the economical functioning of this type of synthesis has not been recognized in the prior art. In the prior art the hydrogen requirements have been supplied autogenously and it is obvious that such hydrogen must be derived from the oleflnic charge or products derived .from the olefinic charge. My experiments have shown that this required hydrogen is derived largely directly from the olefinic charge and that the production of this hydrogen involves the simultaneous formation of very active radicals which accelerate the of low hydrogen-carbon ratios.

'polymerization and condensation of additionalolefines resulting in the formation of relatively large amounts of extremely heavy hydrocarbons By introducin the required amount or an excess of hydrogen with the olefine or oleflnes charged toth'e mixture of aluminum halide and metallic aluminum or activated metallic aluminum I have found that practically quantitative yields of the desired higher alkyl aluminum halides are obtained.

I have found'that it is preferable to use aluminum in the activated state as superior results follow the use of such activated material. Acti-' .vatedaluminum may be prepared by a variety of methods, for example, by amalgamating the .metal superficially by contacting it with an aqueous or alcoholic solution of mercuric chloride. Aluminum-may also be activated by forming a superficial bimetallic couple on the individual aluminum particles by contacting them 7 with an aqueous or alcoholic solution of salts of such metals as copper, cadmium, nickel, iron, zinc -'or the like. The aluminum may also be activated by heating the metal in the presence of a traceof halogen, for example, in the-presence of an amount of halogen equivalentchemically to 1% or-less of the metal. It is preferable to As commercial, aluminum powders are commonly coated withcertain materials such as stearic acid olefines formed being produced 'in addition. The

resulting gas mixture, the reactive components of which consist essentially of normal butenes and hydrogen, is particularly suitable for use as charge in the practice of my invention. As catalysts for accelerating the dehydrogenation of parafilns such materials as activated alumina,

' chromium oxide gel or molybdenum oxide on use activated aluminum 'in finely divided form.

it is advisable and sometimes necessary to remove such coatings prior to activation. This-may be .done bytreating thepowder with asuitable solvent such asether or benzene following which the powder may, if desired, be lightly etched with dilute caustic and then rinsed with water. Even if 'unactivated aluminum is to be used in the-practice of this invention it isadvisable to remove any coatings on the particles prior to such use.

Certain commercial aluminum alloys, for example, the various Lynite alloys containing from 2, to 14% copper, thevarious Dowmetals and the various aluminum-zinc alloys behave in a manner similar to activated aluminum and hence are more suitable for use in this reaction than being presentin approximately equimolecular quantities or, if desired, an excess of the metal or activated metal ,may'be used. As mentioned previously the aluminum metal is preferably used in the activated form. Also the metallic aluminum or activated .metallic aluminum is prefmetallic aluminum itself. It has been found that even when hydrogen is not added with the oleflnic charge, improved results over those disclosed in the prior art are obtained when activated'metallic aluminum is substituted for metallic aluminum, but as has been mentioned previously. best results are obtained when hydrogen is mixed with the olefinic charge and activated aluminum is mixed with the aluminum halide.

In the practice of my invention, any olefine or olefine mixture or any olefine containing mixture may be employed but as a rule it is desirable to use olefines gaseous at ordinary temperatures and pressures. Such olefines are the normal butenes, isobutene, propene, and'cthylene and either an individual olefine or a mixture of two or more olefines may be used. As mentioned previously, the olefine or mixture of olefines is preferably diluted with hydrogen before charging to the mixture of aluminum halide and metallic aluminum or activated aluminum metal and other materials may be present if desired. For example,.the olefine containing gas obtained by the high temperature non-catalytic pyrolysis of propane, which contains ethylene, propene, methane, hydrogen and unconverted propane is very suitable for use in this reaction, especially if additional hydrogen i added to the mixture before charging to the mixture of aluminum halide-and metallic aluminum or activated metallic alu-' minum. Similarly, the gas mixture obtained by the thermal decomposition of butanes, consisting of hydrogen, methane, ethylene, propene, the butenes, ethane, propane and unconverted butanes is very suitable for use in the practice of my invention, especially. if'the'mixture is enriched by the addition of more hydrogen. Gas. mixturesresulting from the catalytic dehydro genation of paraflins are particularly suitable for use in the formation of alkyl aluminum halides. By the catalytic dehydrogenation of normal butane for example, about 85 to 95% of the charge reacting is' converted to normal butenes,

erably employedin the form of a finely divided powder.

be formed into pellets of convenient size or the mixture may be heated, under pressure if ne'ces-.

sary, to melt the aluminum halide which after solidifying with the metallic aluminum or activated-metallic aluminum in suspension is crushed to a convenient size or the molten suspension may be applied to a suitable support such 'as pumice.

In general, the reaction is carried out at superatmospheric pressure, for example at a pressure of from 250 to 3000 pounds per square lnch,-preferably in the pressure range 500 to 1500 pounds.

Fairly low temperatures are employed, for example, C. to 300 0., preferably 100 C. to

an amount of hydrogen equal in volume to the The contacting of the gaseous charge with the 'mixture of aluminum halide and metallic aluminum or activated metallic aluminum may be accomplished by various methods well known to those skilled in the art. For example, the mixture of aluminum halide and metallic aluminum or activated metallic aluminum may bedisposed in a bomb or other similar device and the gaseous charge introduced therein. The bomb or other similar device is then heated to the desired operating temperature and the addition'of the gaseous charge is continued at a rate sufflcient to maintain the pressure at the desired level. When the metal halide-metal mixture-is exhausted, as indicated by cessation of absorption of the gaseous charge, the bomb is cooled, the pressure is released aluminum halides are recovered.

While the desired compounds may be prepared in the above manner it-is generally preferable to operate in a more 'nearly continuous fashion.

The mixture of aluminum halide and metallic" aluminum or activated metallic aluminum, which may be in the pelleted form or in the form prepared by the comminution of the solid resulting from'cooling'a molten mixture of the aluminum .halide bearing the metallic aluminum or activated metallic aluminum in suspension, or mounted on 1 an inert support, is disposed in the reactor. The charge being employed'is continuously passed The mixture of the aluminum halide and metallic aluminum or activated metallic aluminum may be used as such orthe mixture may and the desired alkyl after removing the unreactable components in thermal decomposition zone or a filled with the hal'de-metal mixture and generally charge and the over the halide-metal mixture under the temperature and pressure conditions previously mentioned herein. The-reaction products are cooled and either before or after pressure reduction are separated from unreactedand unreactablecharge. If desired, the unreacted and unreactable charge may be recycled to the reactor, 1 preferably whole or in part. As has been previously suggested herein the unreacted and unreactable components may be sent to a zone, for example a catalytic dehydrogenation zone, for the conversion of additional unreactable components to reactable components following which the resulting mixture is recycled to the reactor. If desired, two reactors may be used in the production of the desired reaction products, the first being used in the production of said products while the other is being being made'ready for placing on stream when the halide-metal mixture in the first reactor has be- In this way continuous production of the desired reaction products is achieved. 0r, if desired, only one reactor may be used and the halide-metal mixture may be added to this continuously or from time to time through a lock or similar device at a rate equal to that at which comeexhaus ted.

.the halide-metal mixture is consumed in the formation of the desired reaction products. As will be obvious to those skilled in the art, most of the aluminum halides exist in the molten state in a portion of the temperature range within which the instant reaction is conducted. For example, a1 um bromide melts just below 100 C. while aluminum. chloride and aluminum iodide melt somewhat below 200 C. Because of this it is possible to conduct the synthesis if dein the molten condition and carrying the metallic aluminum or activated metallic aluminum in suspension therein. For example, a reactor may be used that-is filled with an inert support such as pumice, coke, Raschig rings or thelike. The halide-metal mixture is added continuously-or intermittently to the top of this reactor either as a solid or as a liquid bearing the metal suspended therein. The mixture flows downward over the aforementioned inert supporting material and the rate of addition of the mixture is regulated so as to equal the rateof consumption of the mixture in forming the reaction product. Or, if desired, the aluminum halide may be maintained in the molten state with the metal suspended therein and the charge may be passed through this molten pool, ad-, ditional halide-metal mixture being added fr'om time to time, if desired, to compensate for that entering into the formation of the reaction products.

It is obvious that the nature of the reaction products will vary with the nature or the oleflne nature .of the aluminum halide used in the halide-metal 'mix. To cite a specific example, when the olefin used is ethylene and aluminum chloride is employed in the halidemetal mixture, the resulting product is the two alkyl aluminum halides, ethyl aluminum dichloride anddiethyl aluminum chloride in approximately equimolecular amounts, contaminat j, ed withmore or less heavy condensed ,oifQpoly- 7 merized hydrocarbon liquid. when an .ethylene-= hydrogen mixture. is passed .over aluminum chloride mixed with either metallic aluminum] or. activated metallic aluminum the amount of such contaminating hydrocarbon liquid is quite 75 poses the reaction 7 the liquid phase, consisting isobutane and isobutene present, of a ethyl aluminum chloride in approximately equimolecular proportions, is heated to Ethylene-ispassedjthrough the solution and low but if the is passed ove activated metallic aluminumconsiderably more hydrocarbon liquid forms. The various components present in the reaction mixture may-be separated for example by fractionation, preferably under reduced pressure, but for most purtreatment. ,Alkyl aluminum oxidized by air or are even air and, in addition,

without further halides are rapidly spontaneously inflammable. in react violently with water.

Examples will now be given illustrating the use of the reaction products formed by the practice of the previously described processes as well as the use of other alkyl. aluminum halides. It is to be understood that these examples are illustrative only and in no way limit the scope of'the instant invention.

Example 1.To a reflnery butane cut in essentially of normal butane, normal butenes, is added 5% by weight, based on the olefines mixture consisting essentially of ethyl'aluminum dichloride and diethyl aluminum chloride in approximately equimolecular proportions. The resulting solution is passed through a reactor at-1500 pounds pressure and 200. C. at a rate of 435 cubic feet of charge, measured as a gas at 0 'C. and 760 mm. pressure, per hour per cubic foot of reactor volume. The polymerization of the isdbutylene ispractically quantitative while 85-90% of the normal 'butenes react. In addition, a portion of the isobutane charged disappears, presumably due to alkyiation by'the olefines present. The reaction products are'cooled and either before or after pressure reduction, the gaseous products are separated from the liquids formed. If desired, the latter may be fractionated, that'portion boiling up to 190-200 C. being reserved for use as motor fuel while the portion distilling from 200 C. to 215C. may, if desired, be added to fresh refinery butane in place of an equivalent amount of the alkyl aluminum halide mixture.

Example 2.-To liquid normal butane is added approximately 5 mol percent of a mixture consisting essentially of ethyl aluminum dichloride and diethyl aluminum chloride in approximately equimolecular proportions. maintained in the liquid phase at'25 C. to 50 C. for a period of one week with occasional shaking. At the end of this period some of the original normal butane charge has been isomerized to isobutane.

Example 3.-A mixture consisting of isobutane and 15% butenes and tially of equimolecular proportions -of ethyl. aluminum dischloride and diethyl aluminum chloride, the temperature being 0 C. to 25 C. Branched chain-octanes are. formed through alkylation of the isobutane by the olefines present..

Elauzmplev 4.-1-A mixture of benzene and 10 mol mixture, consisting essentially of dichloride and diethyl aluminum percent of a about 50 C. to 75 C.

Example, ,5.- mixture consisting essentially di made and diethyl chloride in approximately equimolecmixture can be used as such The mixture isobutenes is passed with stirring through a mixture consisting essenular proportions is diluted with diethyl ether following which boron fluoride or the boron fluoride-diethyl ether complex is added slowly with cooling. The stoichiometric amount of boron fluoride or somewhat less is employed based on the formation of triethyl boron. When addition is complete the reaction mixture is slowly heated to 50 C. to 70 C. andmaintained at this temperature for two hours. If desired, the

' may be had to my copending application Serial Number 307,447, filed December 4, 1939, Patent Example 6.About 5% by weight of a mixture consisting essentially of ethyl aluminum dichloride and diethyl aluminum chloride in approximately equimolecular proportions is added to wax distillate having a boiling range of about 60 C. to -240 C. and made by the thermal cracking of parafiin wax under vapor phase conditions, for .example at a pressure of 25 pounds per square inch and a temperature of 525 C. The reaction mixture is heated to 50 C. and stirred at this temperature for 24 hours. At the end of this time the resulting mixture is cooled and decomposed by the slow addition of dilute mineral acid. The organic layer is separated and steam distilled. Lubricating oil bottoms are obtained having a high viscosity index. Instead of wax distillate, a corresponding cut from the hydrocarbon mixture obtained by the reduction of carbon monoxide withhydrogen in the presence of a nickel catalyst may be employed withsimilar results. If desired, in the polymerization reaction the catalyst may be promoted by adding a trace of water, a hydrogen halide or alkyl halide or the like to the reaction mixture.

Example 7.-Silica gel is saturated with a mixture consisting essentially of ethyl aluminum dichloride and diethyl aluminum chloride in approximately equimolecular quantities. The resulting saturated solid is treated withan inert gas such as nitrogen containing water vapor. The product formed is an excellent catalyst for the cracking of hydrocarbons.

While all the above examples have been described with' respect to a mixture containing ethyl aluminum'dichloride and diethyl aluminum chloride in approximately equimolecular proportions it is to be understood that other alkyl aluminum halides or mixtures thereof may be used with similar results. In fact, insome cases, it is preferable'but not necessary to use other alkyl aluminum halides. For example, when using alkyl aluminumhalides as polymerizing catalysts or alkylation catalysts it is preferable to use alkyl aluminum halides, the alkyl group or groups of which contain the same number of product is contaminated with more or less of the various ethyl benze'nes andethyl isopropyl benactivated metallic aluminum.

2. The process for preparing alkyl aluminum halides higher than the methyl derivatives comprising contacting an oleflne with an aluminum halidein intimate association with activated ing the resulting product comprising an olefi'ne and hydrogen with an aluminum halide in intimate association with a material from the group consisting of metallic aluminum and activated metallic aluminum.

4. The process for preparing alkyl aluminum halides higher than the methyl derivatives comprising catalytically dehydrogenating a gaseous parafiin hydrocarbon higher than methane and contacting the resulting product comprising an oleflne and hydrogen with an aluminum halide in intimate association with a material from the group consisting of metallic aluminum and activated metallic aluminum.

5. The process for-preparing alkyl aluminum halides higher than the methyl derivatives comprising catalytically dehydrogenating a hydrocarbon higher than methane, contacting the resulting product comprising an oleflne and hydrogen with an aluminum halide in intimate association with a paraflln material selected from the group consisting of metallic aluminum and activated metallic aluminum separating uncon verted and unconvertible components from the reaction mixture and recycling said unconverted and unconvertible components to the catalytic dehydrogenation zone.

6. The process-for preparing alkyl aluminum halides higher than the methyl derivatives comprising catalytically dehydrogenating a gaseous paraflin hydrocarbon higher than methane, contacting the resulting product comprising an olecarbon atoms as the oleflnes being polymerized or being employed in alkylation. In these, andsimilar reactions, the alkyl aluminum halides halide or diisopropyl aluminum halide or mixtures thereof as catalyst various isopropyl ben- .zenes are formed but if, on the' other han'd,-ethyl aluminmdihalide or diethyl aluminum halide or mixtures thereof is used as catalyst the major.

fine and'hydrogen with an aluminum halide in intimate association with a material selected .from the group consisting of metallic aluminum and activated metallic aluminum, separating unconverted and unconvertible gaseous components from the liquid reaction product and recycling said unconverted and unconvertible gaseous components to the catalytic dehydrogenation zone.

7. The process for preparing alkyl aluminum halides higher than the methyl derivatives comprising thermally decomposing a hydrocarbon higher than methane and contacting the resulting mixture with an aluminum halidein intimate association with activated metallic alu- 8. Theprocess for preparing alkyl halides higher than the methyl derivatives comprising cracking a' hydrocarbonhigher than methane, adding hydrogen to the resulting product in an amount sufilcient to give an' olefine-hydrogen ratio by volume of not more than two and contacting the resulting mixture with an aluminum halide in intimate association with a material selected from the group consisting of metallic aluminum and activated metallic aluminum. v w

9. The process for preparing alkyl aluminum halides higher than the methyl derivatives comprising thermally decomposi'ng a hydrocarbon higher than methane, contacting the resulting] product with an aluminum halide in intimate association with activated metallic aluminum, separating unconverted and unconvertible components from the recycling said unconverted and unconvertible components to the thermal decomposition zone.

10. The process for preparing alkyl aluminum halides higher than the methyl derivatives comprising cracking a hydrocarbon higher than methane, adding hydrogen to the resulting product in an amount suflicient to give an olefinehydrogen volume ratio of not more than two, contacting the resulting mixture with an aluminum halide in intimate association with a ma-.

halides higher than the methyl derivatives comprising cracking a' gaseous hydrocarbon higher than methane, adding hydrogen to the resulting product in an amount suflicient to givean olefineresulting reaction mixture andhydrogen volume ratio of not more than two and contacting the resulting mixture with an alu- 'minum halidein intimate association with a material selected from the group consisting of Inc-'- tallic aluminum and activated metallic aluminum. v

13'. The process for preparing alkyl aluminumhalides higher than the methyl derivatives comprising thermally decomposing agaseous hydrominum,

for preparing alkyl aluminum carbon higher than methane, contacting the resulting mixture with an aluminum-halidein intimate association.

with activated metallic aluminum, separating the unconverted and unconvertible'gaseous components from the liquid reaction product, and recycling said unconverted and unconvertible gaseous components to the thermaldecomposition zon 14. The process halides higher than the methyl derivatives comprisingcracking a gaseous-hydrocarbon higher than methane, adding hydrogen product in an amount suflicient to give an olefinehydrogen volume ratio of not more than two,

contacting the resulting mixture with an aluminum halide in intimate association with a material selected from the group consistingof metallic aluminum and activated metallic aluseparating unconverted and unconvertible gaseous components from the liquid reaction product and recycling said unconverted and unconvertible gaseous components to the cracking zone.

15. The process for preparing alkyl aluminum halides higher than the methyl derivatives comprising contacting a fluid containing-an olefine and hydrogen with analuminum mate'association with metallic aluminum.-

16. The process for preparing alkyl'aluminum halides higher than-the methyl derivatives comprising contacting an olefine and hydrogen with an aluminum halide inintimate association with activated metallic aluminum.

ROBERT F'. RUTHRUFF.

for preparing allgyl aluminum to the resulting halide ini'nti- I 

